This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 1) Glutamine?dependent NAD+ synthetase catalyzes the last step of the de novo and recycling pathways in NAD+ biosynthesis. This enzyme is essential for survival of replicating and non-replicating M. tuberculosis and as such it is an attractive drug target. In humans NAD synthetase independent pathways participate in NAD biosynthesis. We are working on the structural and kinetic characterizations of the H. sapiens and M. tuberculosis enzymes. 2) Pyrrolobenzodiazepine are natural products with strong antitumor properties. We are studying the biosynthesis of these compounds and we have identified two enzymes that catalyze unusual chemical reactions and that have no homologous in the PBD database. Therefore, the second project includes the structural determination of these unprecedented enzymes involved in pyrrolobenzodiazepine biosynthesis.